The role of viscous deformation in the machining of polymers

This study aims to evaluate the machinability of typical thermoplastic and thermosetting polymers and understand the effect of their viscous properties on surface integrity, chip formation and machining forces. The interaction between the strain rate and temperature during machining was particularly addressed. It was found that the viscous deformation of a polymer plays a decisive role in determining the quality of a machined surface. To minimize the surface roughness, for instance, the machining conditions must be selected in such a way that the material removal deformation falls in the regime without visco-plastic scaling/tearing and brittle cracking. The optimal machining condition must be based on the polymer properties, such as the glass transition temperature, fracture toughness and molecular mobility. The shear stress in the shear plane of chipping is a good measure of the coupled effect of strain rate and temperature rise. In addition, the study discovered two new types of chips whose deformation and curling were in close relation to the surface integrity of the machined components.